Apparatus and methods for reducing embolization during treatment of carotid artery disease

ABSTRACT

Methods and apparatus are provided for removing emboli during an angioplasty, stenting or surgical procedure comprising a catheter having an occlusion element, an aspiration lumen, and a blood outlet port in communication with the lumen, a guide wire having a balloon, a venous return catheter with a blood inlet port, and tubing that couples the blood outlet port to the blood inlet port. Apparatus is also provided for occluding the external carotid artery to prevent reversal of flow into the internal carotid artery. The pressure differential between the artery and the vein provides reverse flow through the artery, thereby flushing emboli. A blood filter may optionally be included in-line with the tubing to filter emboli from blood reperfused into the patient.

REFERENCE TO RELATED APPLICATIONS

[0001] The present application is a continuation-in-part of U.S. patentapplication Ser. No. 09/333,074, filed Jun. 14, 1999, which is acontinuation-in-part of International Application PCT/US99/05469, filedMar. 12, 1999, which is a continuation-in-part of U.S. patentapplication Ser. No. 09/078,263, filed Mar. 5, 1998.

FIELD OF THE INVENTION

[0002] This invention relates to apparatus and methods for protectingagainst embolization during vascular interventions, such as carotidartery angioplasty and endarterectomy. More particularly, the apparatusand methods of the present invention induce substantially continuousretrograde flow through the internal carotid artery during treatmentduring an interventional procedure, without significant blood loss.

BACKGROUND OF THE INVENTION

[0003] Carotid artery stenoses typically manifest in the common carotidartery, internal carotid artery or external carotid artery as apathologic narrowing of the vascular wall, for example, caused by thedeposition of plaque, that inhibits normal blood flow. Endarterectomy,an open surgical procedure, traditionally has been used to treat suchstenosis of the carotid artery.

[0004] An important problem encountered in carotid artery surgery isthat emboli may be formed during the course of the procedure, and theseemboli can rapidly pass into the cerebral vasculature and cause ischemicstroke.

[0005] In view of the trauma and long recuperation times generallyassociated with open surgical procedures, considerable interest hasarisen in the endovascular treatment of carotid artery stenosis. Inparticular, widespread interest has arisen in transforminginterventional techniques developed for treating coronary arterydisease, such as angioplasty and stenting, for use in the carotidarteries. Such endovascular treatments, however, are especially prone tothe formation of emboli.

[0006] Such emboli may be created, for example, when an interventionalinstrument, such as a guide wire or angioplasty balloon, is forcefullypassed into or through the stenosis, as well as after dilatation anddeflation of the angioplasty balloon or stent deployment. Because suchinstruments are advanced into the carotid artery in the same directionas blood flow, emboli generated by operation of the instruments arecarried directly into the brain by antegrade blood flow.

[0007] Stroke rates after carotid artery stenting have widely varied indifferent clinical series, from as low as 4.4% to as high as 30%. Onereview of carotid artery stenting including data from twenty-four majorinterventional centers in Europe, North America, South America and Asia,had a combined initial failure and combined mortality/stroke rate ofmore than 7%. Cognitive studies and reports of intellectual changesafter carotid artery stenting indicate that embolization is a commonevent causing subclinical cerebral damage.

[0008] Several previously known apparatus and methods attempt to removeemboli formed during endovascular procedures by trapping or suctioningthe emboli out of the vessel of interest. These previously knownsystems, however, provide less than optimal solutions to the problems ofeffectively removing emboli.

[0009] Solano et al. U.S. Pat. No. 4,921,478 describes cerebralangioplasty methods and devices wherein two concentric shafts arecoupled at a distal end to a distally-facing funnel-shaped balloon. Alumen of the innermost shaft communicates with an opening in thefunnel-shaped balloon at the distal end, and is open to atmosphericpressure at the proximal end. In use, the funnel-shaped balloon isdeployed proximally (in the direction of flow) of a stenosis, occludingantegrade flow. An angioplasty balloon catheter is passed through theinnermost lumen and into the stenosis, and then inflated to dilate thestenosis. The patent states that when the angioplasty balloon isdeflated, a pressure differential between atmospheric pressure and theblood distal to the angioplasty balloon causes a reversal of flow in thevessel that flushes any emboli created by the angioplasty balloonthrough the lumen of the innermost catheter.

[0010] While a seemingly elegant solution to the problem of emboliremoval, several drawbacks of the device and methods described in theSolano et al. patent seem to have lead to abandonment of that approach.Chief among these problems is the inability of that system to generateflow reversal during placement of the guide wire and the angioplastyballoon across the stenosis. Because flow reversal does not occur untilafter deflation of the angioplasty balloon, there is a substantial riskthat any emboli created during placement of the angioplasty balloon willtravel too far downstream to be captured by the subsequent flowreversal. It is expected that this problem is further compounded becauseonly a relatively small volume of blood is removed by the pressuredifferential induced after deflation of the angioplasty balloon.

[0011] Applicant has determined another drawback of the method describedin the Solano patent: deployment of the funnel-shaped balloon in thecommon carotid artery (“CCA”) causes reversal of flow from the externalcarotid artery (“ECA”) into the internal carotid artery (“ICA”), due tothe lower flow impedance of the ICA. Consequently, when a guide wire orinterventional instrument is passed across a lesion in either the ECA orICA, emboli dislodged from the stenosis are introduced into the bloodflow and carried into the cerebral vasculature via the ICA.

[0012] The insufficient flow drawback identified for the system of theSolano patent is believed to have prevented development of a commercialembodiment of the similar system described in EP Publication No. 0 427429. EP Publication No. 0 427 429 describes use of a separate balloon toocclude the ECA prior to crossing the lesion in the ICA. However, likeSolano, that publication discloses that flow reversal occurs only whenthe dilatation balloon in the ICA is deflated.

[0013] Chapter 46 of Interventional Neuroradioloy: strategies andpractical techniques (J. J. Connors & J. Wojak, 1999), published bySaunders of Philadelphia, Pa., describes using a coaxial balloonangioplasty system for patients having with proximal ICA stenoses. Inparticular, a small, deflated occlusion balloon on a wire is introducedinto the origin of the ECA, and a guide catheter with a deflatedocclusion balloon is positioned in the CCA just proximal to the originof the ECA. A dilation catheter is advanced through a lumen of the guidecatheter and dilated to disrupt the stenosis Before deflation of thedilation catheter, the occlusion balloons on the guide catheter and inthe ECA are inflated to block antegrade blood flow to the brain. Thedilation balloon then is deflated, the dilation catheter is removed, andblood is aspirated from the ICA to remove emboli.

[0014] Applicant has determined that cerebral damage still may resultfrom the foregoing previously known procedure, which is similar to thatdescribed in EP Publication No. 0 427 429, except that the ICA isoccluded prior to the ECA. Consequently, both of these previously knownsystems and methods suffer from the same drawback—the inability togenerate flow reversal at sufficiently high volumes during placement ofthe guide wire and dilation catheter across the stenosis. Both methodsentail a substantial risk that any emboli created during placement ofthe balloon will travel too far downstream to be captured by the flowreversal.

[0015] Applicants note, irrespective of the method of aspirationemployed with the method described in the foregoing InterventionalNeuroradiology article, substantial drawbacks are attendant. If, forexample, natural aspiration is used (i.e., induced by the pressuregradient between the atmosphere and the artery), then only a relativelysmall volume of blood is expected to be removed by the pressuredifferential induced after deflation of the angioplasty balloon. If, onthe other hand, an external pump is utilized, retrieval of thesedownstream emboli may require a flow rate that cannot be sustained formore than a few seconds, resulting insufficient removal of emboli.

[0016] Furthermore, with the dilation balloon in position, the occlusionballoons are not inflated until after inflation of the dilation balloon.Microemboli generated during advancement of the dilation catheter intothe stenosed segment may therefore be carried by retrograde blood flowinto the brain before dilation, occlusion, and aspiration are evenattempted.

[0017] A still further drawback of both the device in EP Publication No.0 427 429 and the Interventional Neuroradiology device is that, if theyare used for placing a stent in the ICA instead of for ICA angioplasty,the stent often extends beyond the bifurcation between the ECA and theICA. The occlusion balloon placed by guide wire in the ECA may snag thestent during retrieval. Emergency surgery may then be required to removethe balloon.

[0018] Imran U.S. Pat. No. 5,833,650 describes a system for treatingstenoses that comprises three concentric shafts. The outermost shaftincludes a proximal balloon at its distal end that is deployed proximalof a stenosis to occlude antegrade blood flow. A suction pump then drawssuction through a lumen in the outermost shaft to cause a reversal offlow in the vessel while the innermost shaft is passed across thestenosis. Once located distal to the stenosis, a distal balloon on theinnermost shaft is deployed to occlude flow distal to the stenosis.Autologous blood taken from a femoral artery using an extracorporealblood pump is infused through a central lumen of the innermost catheterto provide continued antegrade blood flow distal to the distal balloon.The third concentric shaft, which includes an angioplasty balloon, isthen advanced through the annulus between the innermost and outermostcatheters to dilate the stenosis.

[0019] Like the device of the Solano patent, the device of the Imranpatent appears to suffer the drawback of potentially dislodging embolithat are carried into the cerebral vasculature. In particular, once thedistal balloon of Imran's innermost shaft is deployed, flow reversal inthe vasculature distal to the distal balloon ceases, and the bloodperfused through the central lumen of the innermost shaft establishesantegrade flow. Importantly, if emboli are generated during deploymentof the distal balloon, those emboli will be carried by the perfusedblood directly into the cerebral vasculature, and again pose a risk ofischemic stroke. Moreover, there is some evidence that reperfusion ofblood under pressure through a small diameter catheter may contribute tohemolysis and possible dislodgment of emboli.

[0020] In applicant's co-pending U.S. patent application Ser. No.09/333,074, filed Jun. 14, 1999, which is incorporated herein byreference, applicant described the use of external suction to induceregional reversal of flow. That application further described thatintermittently induced regional flow reversal overcomes the drawbacks ofnaturally-aspirated systems such as described hereinabove. However, theuse of external suction may in some instances result in flow rates thatare too high to be sustained for more than a few seconds. In addition,continuous use of an external pump may result in excessive blood loss,requiring infusion of non-autologous blood and/or saline that causeshemodilution, reduced blood pressure, or raise related safety issues.

[0021] In view of these drawbacks of the previously known emboli removalsystems, it would be desirable to provide methods and apparatus forremoving emboli from within the carotid arteries during interventionalprocedures, such as angioplasty or carotid stenting, that reduce therisk that emboli are carried into the cerebral vasculature.

[0022] It also would be desirable to provide methods and apparatus forremoving emboli from within the carotid arteries during interventionalprocedures, such as angioplasty or carotid stenting, that providesubstantially continuous low retrograde blood flow from the treatmentzone, thereby reducing the risk that emboli are carried into thecerebral vasculature.

[0023] It further would be desirable to provide emboli removal methodsand apparatus that prevent the development of reverse flow from the ECAand antegrade into the ICA once the CCA has been occluded, therebyenhancing the likelihood that emboli generated by a surgical orinterventional procedure are effectively removed from the vessel.

[0024] It still further would be desirable to provide an occlusionballoon on a guide wire for placement in the ECA during stenting of theICA that mitigates the risk of snagging the stent during removal.

[0025] It also would be desirable to provide methods and apparatus forremoving emboli during a carotid stenting procedure that enablefiltering of emboli and reduced blood loss.

SUMMARY OF THE INVENTION

[0026] In view of the foregoing, it is an object of this invention toprovide methods and apparatus for removing emboli from within thecarotid arteries during interventional procedures, such as angioplastyor carotid stenting, that reduce the risk that emboli are carried intothe cerebral vasculature.

[0027] It also is an object of the present invention to provide methodsand apparatus for removing emboli from within the carotid arteriesduring interventional procedures, such as angioplasty or carotidstenting, that provide substantially continuous low retrograde bloodflow from the treatment zone, thereby reducing the risk that emboli arecarried into the cerebral vasculature.

[0028] It is another object of the present invention to provide emboliremoval methods and apparatus that prevent the development of reverseflow between the ECA and ICA once the common carotid artery has beenoccluded, thereby enhancing the likelihood that emboli generated by asurgical or interventional procedure are effectively removed from thevessel.

[0029] It is a further object of this invention to provide methods andapparatus for an occlusion balloon on a guide wire for placement in theECA during stenting of the ICA that mitigates the risk of snagging thestent during removal.

[0030] It is yet another object of the present invention to providemethods and apparatus for removing emboli during a carotid stentingprocedure that enable filtering of emboli and reduced blood loss.

[0031] The foregoing objects of the present invention are accomplishedby providing interventional apparatus comprising an arterial catheter,an occlusion balloon disposed on a guide wire, a venous return catheter,and optionally a blood filter. The arterial catheter has proximal anddistal ends, an aspiration lumen extending therebetween, an occlusionelement disposed on the distal end, and a hemostatic port and bloodoutlet port disposed on the proximal end that communicate with theaspiration lumen. The aspiration lumen is sized so that aninterventional instrument, e.g., an angioplasty catheter or stentdelivery system, may be readily advanced therethrough to the site of astenosis in either the ECA (proximal to the balloon) or the ICA.

[0032] In accordance with the principles of the present invention, thearterial catheter is disposed in the CCA proximal of the ICA/ECAbifurcation, the occlusion balloon on the guide wire is disposed in theECA to occlude flow reversal from the ECA to the ICA, and the bloodoutlet port of the arterial catheter is coupled to the venous returncatheter, with or without the blood filter disposed therebetween. Higherarterial than venous pressure, especially during diastole, permitssubstantially continuous flow reversal in the ICA during the procedure(other than when a dilatation balloon is inflated), thereby flushingblood containing emboli from the vessel. The blood is filtered andreperfused into the body through the venous return catheter.

[0033] Methods of using the apparatus of the present invention are alsoprovided.

BRIEF DESCRIPTION OF THE DRAWINGS

[0034] Further features of the invention, its nature and variousadvantages will be more apparent from the accompanying drawings and thefollowing detailed description of the preferred embodiments, in which:

[0035]FIGS. 1A and 1B are schematic views of previously known emboliprotection systems;

[0036]FIG. 2 is a schematic view of the emboli protection system of thepresent invention;

[0037] FIGS. 3A-3D are, respectively, a schematic view, and detailedside and sectional views of the distal end of an interventional deviceof the present invention;

[0038]FIGS. 4A and 4B are views of the distal end of an alternativeinterventional device suitable for use in the system of the presentinvention; and

[0039] FIGS. 5A-5D illustrate a method of using the system of FIG. 3 inaccordance with the principles of the present invention;

[0040] FIGS. 6A-6B are, respectively, a schematic view and across-sectional view of an alternative embodiment of the device of FIGS.3;

[0041] FIGS. 7A-7B are, respectively, a schematic view of an alternativeembodiment of the guide wire balloon elements of the device of FIGS. 3,and a method of using the alternative embodiment.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0042] Referring to FIGS. 1A and 1B, drawbacks of previously knownemboli removal catheters are described with reference to performingpercutaneous angioplasty of stenosis S in common carotid artery CCA.

[0043] With respect to FIG. 1A, drawbacks associated withnaturally-aspirated emboli removal systems, such as described in theabove-mentioned patent to Solano and European Patent Publication, aredescribed. No flow reversal is induced by those systems until afterballoon 10 of angioplasty catheter 11 first is passed across thestenosis, inflated, and then deflated. However, applicant has determinedthat once member 15 of emboli removal catheter 16 is inflated, flowwithin the ECA reverses and provides antegrade flow into the ICA, due tothe lower hemodynamic resistance of the ICA. Consequently, emboli Egenerated while passing guide wire 20 or catheter 11 across stenosis Smay be carried irretrievably into the cerebral vasculature—before flowin the vessel is reversed and directed into the aspiration lumen ofemboli removal catheter 16 by opening the proximal end of the aspirationlumen to atmospheric pressure Furthermore, natural-aspiration may notremove an adequate volume of blood to retrieve even those emboli thathave not yet been carried all the way into the cerebral vasculature.

[0044] In FIG. 1B, system 17 described in the above-mentioned patent toImran is shown. As described hereinabove, deployment of distal balloon18, and ejection of blood out of the distal end of the inner catheter,may dislodge emboli from the vessel wall distal to balloon 18. Theintroduction of antegrade flow through inner catheter 19 is expectedonly to exacerbate the problem by pushing the emboli further into thecerebral vasculature. Thus, while the use of positive suction in theImran system may remove emboli located in the confined treatment fielddefined by the proximal and distal balloons, such suction is notexpected to provide any benefit for emboli dislodged distal of distalballoon 18.

[0045] Referring now to FIG. 2, apparatus and methods of the presentinvention are described. Apparatus 30 comprises catheter 31 having anaspiration lumen and occlusion element 32, and guide wire 35 havinginflatable balloon 36 disposed on its distal end. In accordance with theprinciples of the present invention, antegrade blood flow is stoppedwhen both occlusion element 32 in the CCA and inflatable balloon 36 aredeployed. Furthermore, the aspiration lumen of catheter 31 is connectedto a venous return catheter (described hereinbelow), disposed, forexample, in the patient's femoral vein. In this manner a substantiallycontinuous flow of blood is induced between the treatment site and thepatient's venous vasculature. Because flow through the artery is towardscatheter 31, any emboli dislodged by advancing a guide wire orangioplasty catheter 33 across stenosis S causes the emboli to beaspirated by catheter 31.

[0046] Unlike the previously known naturally-aspirated systems, thepresent invention provides substantially continuous retrograde bloodflow through eh ICA while preventing blood from flowing retrograde inthe ECA and antegrade into the ICA, thereby preventing emboli from beingcarried into the cerebral vasculature. Because the apparatus and methodsof the present invention “recycle” emboli-laden blood from the arterialcatheter through the blood filter and to the venous return catheter, thepatient experiences significantly less blood loss.

[0047] Referring now to FIG. 3A, embolic protection apparatus 40constructed in accordance with the principles of the present inventionis described. Apparatus 40 comprises arterial catheter 41, guide wire45, venous return line 52, tubing 49 and optional blood filter 50.

[0048] Catheter 41 includes distal occlusion element 42, proximalhemostatic port 43, e.g., a Touhy-Borst connector, inflation port 44,and blood outlet port 48. Guide wire 45 includes balloon 46 that isinflated via inflation port 47. Tubing 49 couples blood outlet port 48to filter 50 and blood inlet port 51 of venous return line 52.

[0049] Guide wire 45 and balloon 46 are configured to pass throughhemostatic port 43 and the aspiration lumen of catheter 41 (see FIGS. 3Cand 3D), so that the balloon may be advanced into and occlude the ECA.Port 43 and the aspiration lumen of catheter 41 are sized to permitadditional interventional devices, such as angioplasty ballooncatheters, atherectomy devices and stent delivery systems to be advancedthrough the aspiration lumen when guide wire 45 is deployed.

[0050] Guide wire 45 preferably comprises a small diameter flexibleshaft having an inflation lumen that couples inflatable balloon 46 toinflation port 47. Inflatable balloon 46 preferably comprises acompliant material, such as described hereinabove with respect toocclusion element 42 of emboli removal catheter 41.

[0051] Venous return line 52 includes hemostatic port 53, blood inletport 51 and a lumen that communicates with ports 53 and 51 and tip 54.Venous return line 52 may be constructed in a manner per se known forvenous introducer catheters. Tubing 49 may comprise a suitable length ofa biocompatible material, such as silicone. Alternatively, tubing 49 maybe omitted and blood outlet port 48 of catheter 41 and blood inlet port51 of venous return line 52 may be lengthened to engage either end offilter 50 or each other.

[0052] With respect to FIGS. 3B and 3C, distal occlusion element 42comprises expandable bell or pear-shaped balloon 55. In accordance withmanufacturing techniques which are known in the art, balloon 55comprises a compliant material, such as polyurethane, latex orpolyisoprene which has variable thickness along its length to provide abell-shape when inflated. Balloon 55 is affixed to distal end 56 ofcatheter 41, for example, by gluing or a melt-bond, so that opening 57in balloon 55 leads into aspiration lumen 58 of catheter 41. Balloon 55preferably is wrapped and heat treated during manufacture so that distalportion 59 of the balloon extends beyond the distal end of catheter 41and provides an atraumatic tip or bumper for the catheter.

[0053] As shown in FIG. 3D, catheter 41 preferably comprises inner layer60 of low-friction material, such as polytetrafluoroethylene (“PTFE”),covered with a layer of flat stainless steel wire braid 61 and polymercover 62 (e.g., polyurethane, polyethylene, or PEBAX). Inflation lumen63 is disposed within polymer cover 62 and couples inflation port 44 toballoon 55. In a preferred embodiment of catheter 41, the diameter oflumen 58 is 7 Fr, and the outer diameter of the catheter isapproximately 9 Fr.

[0054] Referring now to FIGS. 4A and 4B, an alternative embodiment ofocclusion element 42 of the system of FIG. 3A is described. In FIGS. 4Aand 4B, occlusion element 42 of emboli removal catheter 41 comprisesself-expanding wire basket 65 covered with elastomeric polymer 66, suchas latex, polyurethane or polyisoprene. Alternatively, a tightly knitself-expanding wire mesh may be used, with or without an elastomericcovering.

[0055] Catheter 41 is surrounded by movable sheath 67. Catheter 41 isinserted transluminally with sheath 67 in a distalmost position, andafter basket 65 has been determined to be in a desired position proximalto a stenosis, sheath 67 is retracted proximally to cause basket 65 todeploy. Upon completion of the procedure, basket 65 is again collapsedwithin sheath 67 by moving the sheath to its distalmost position.Operation of the system of FIG. 3A using the emboli removal catheter ofFIGS. 4A and 4B is similar to that described hereinbelow for FIGS.5A-5D, except that the occlusion element self-expands when sheath 67 isretracted, rather than by infusing an inflation medium to balloon 55.

[0056] Referring now to FIGS. 5A-5D, use of the apparatus of FIGS. 3 inaccordance with the methods of the present invention is described. InFIGS. 5, stenosis S is located in internal carotid artery ICA above thebifurcation between the internal carotid artery ICA and the externalcarotid artery ECA. In a first step, catheter 41 is inserted, eitherpercutaneously and transluminally or via a surgical cut-down, to aposition proximal of stenosis S, without causing guide wire 45 to crossthe stenosis. Balloon 55 of distal occlusion element 42 is theninflated, preferably with a radiopaque contrast solution, via inflationport 44. As seen in FIG. 5A, this creates reversal of flow from theexternal carotid artery ECA into the internal carotid artery ICA.

[0057] Venous return line 52 then is introduced into the patient'sfemoral vein, either percutaneously or via a surgical cut-down. Filter50 is then coupled between blood outlet port 48 of catheter 41 and bloodinlet port 51 of venous return line 52 using tubing 49, and any air isremoved from the line. Once this circuit is closed, negative pressure inthe venous catheter during diastole will establish a low rate continuousflow of blood through aspiration lumen 58 of catheter 41, as seen inFIG. 5B, to the patient's vein via venous return line 52.

[0058] This low rate continuous flow due to the difference betweenvenous pressure and arterial pressure will continue throughout theinterventional procedure. Specifically, blood passes through aspirationlumen 58 and blood outlet port 48 of catheter 41, through biocompatibletubing 49 to filter 50, and into blood inlet port 51 of venous returnline 52, where it is reperfused into the remote vein. Filtered embolicollect in filter 50 and may be studied and characterized uponcompletion of the procedure.

[0059] Continuous blood flow (except during inflation of any dilatationinstruments) with reperfusion in accordance with the present inventionprovides efficient emboli removal with significantly reduced blood loss.Alternatively, filter 50 may be omitted, in which case emboli removedfrom the arterial side will be introduced into the venous side, andeventually captured in the lungs. Because of a low incidence of septaldefects, which could permit such emboli to cross-over to the leftventricle, the use of filter 50 is preferred.

[0060] Referring to FIG. 5C, with balloon 55 of occlusion element 42inflated and a retrograde flow established in the ICA, guide wire 45 andballoon 46 are advanced through aspiration lumen 58. When balloon 46 isdisposed within the ECA, as determined, e.g., using a fluoroscope and aradiopaque inflation medium injected into balloon 46, balloon 46 isinflated. Occlusion of the ECA prevents the development of reverse flowin the ECA from causing antegrade flow in the ICA. Anotherinterventional instrument, such as conventional angioplasty ballooncatheter 71 having balloon 72, is loaded through hemostatic port 43 andaspiration lumen 58 and positioned within the stenosis. Hemostatic port43 is closed and instrument 71 is actuated to disrupt the plaque formingstenosis S.

[0061] As seen in FIG. 5D, upon completion of the angioplasty portion ofthe procedure using catheter 71, balloon 72 is deflated Throughout theprocedure, except when the dilatation balloon is fully inflated, thepressure differential between the blood in the ICA and the venouspressure causes blood in ICA to flow in a retrograde direction in theICA into aspiration lumen 58 of emboli removal catheter 41, therebyflushing any emboli from the vessel. The blood is filtered andreperfused into the patient's vein.

[0062] Optionally, increased volumetric blood flow through theextracorporeal circuit may by achieved by attaching an external pump,such as a roller pump, to tubing 49. If deemed beneficial, the externalpump may be used in conjunction with device 40 at any point during theinterventional procedure. Instrument 71, guide wire 45, emboli removalcatheter 41, and venous return line 52 are then removed from thepatient, completing the procedure.

[0063] As set forth above, the method of the present invention protectsagainst embolization, first, by preventing the reversal of blood flowfrom the ECA to the ICA when distal occlusion element 42 is inflated,and second, by providing continuous, low volume blood flow from thecarotid artery to the remote vein in order to filter and flush anyemboli from the vessel and blood stream. Advantageously, the method ofthe present invention permits emboli to be removed with little bloodloss, because the blood is filtered and reperfused into the patient.Furthermore, continuous removal of blood containing emboli preventsemboli from migrating too far downstream for aspiration.

[0064] Referring now to FIGS. 6, apparatus 140 constructed in accordancewith the present invention is described. Apparatus 140 is an alternativeembodiment of apparatus 40 described hereinabove and comprises arterialcatheter 141 having distal occlusion element 142, proximal hemostaticport 143, inflation port 144 and blood outlet port 148. Guide wire 145includes balloon 146 that is inflated via inflation port 147.Biocompatible tubing 149 couples blood outlet port 148 to filter 150 andto blood inlet port 151 of venous return line 152. Arterial catheter141, guide wire 145, venous return line 152 and tubing 149 areconstructed as described hereinabove, except as noted below.

[0065] Guide wire 145 and balloon 146 are configured to pass throughguide wire lumen 164 of catheter 141 (see FIG. 6B), so that the balloonmay be advanced into and occlude the ECA. Additionally, catheter 141comprises aspiration lumen 158 which is sized to permit interventionaldevices, such as angioplasty balloon catheters, atherectomy devices andstent delivery systems to be advanced through port 143 and theaspiration lumen. As shown in FIG. 6B, the key difference betweencatheters 41 and 141 lies in the method of advancing the guide wirethrough the catheter: guide wire 45 is advanced through the aspirationlumen of catheter 41, whereas guide wire 145 is advanced throughseparate guide wire lumen 164 of catheter 141.

[0066] Catheter 141 preferably is constructed from inner layer 160 oflow-friction material, such as polytetrafluoroethylene (“PTFE”), coveredwith a layer of flat stainless steel wire braid 161, and polymer cover162 (e.g., polyurethane, polyethylene, or PEBAX). Inflation lumen 163 isdisposed within polymer cover 162 and couples inflation port 144 toocclusion element 142. Guide wire lumen 164 also is disposed withinpolymer cover 142, and is sized to permit guide wire 145 and balloon 146to pass therethrough. In a preferred embodiment of catheter 141, thediameter of inflation lumen 163 is 0.014″, the diameter of guide wirelumen 164 is 0.020″, and the diameter of lumen 158 is 7 Fr. To retain anouter catheter diameter in the preferred embodiment of approximately 9Fr., the thickness of the catheter wall varies around the circumferencefrom a maximum of 0.026″ at the location of guide wire lumen 164 to aminimum of 0.005″ 180 degrees away.

[0067] Referring now to FIGS. 7, an alternative embodiment of the guidewire occlusion apparatus of the present invention is described.Occlusion apparatus 200 comprises guide wire 201, occlusion balloon 202,inflation lumen 203, and wedge 204. Wedge 204 may comprise a resilientmaterial, such as a polymer or resilient wire, and reduces the risk thatballoon 202 will snag on a stent that extends beyond the bifurcation ofthe ICA and ECA.

[0068] For the reasons described hereinabove, it is desirable whenperforming a stenting procedure in the ICA to occlude the ECA, toprevent flow reversal from the ECA and into the ICA. Accordingly, anocclusion balloon on a guide wire is placed in the ECA and inflated toblock that artery. A stent then may be placed in the ICA to ensureproper blood flow to the ICA. It is often desirable, however, for suchstents to extend beyond the bifurcation between the ECA and the ICA.Consequently, when the occlusion balloon on the guide wire is deflatedand withdrawn from the ECA, there is a risk that the balloon may snagthe stent. In such cases, emergency surgery is often required to removethe balloon.

[0069] Referring now to FIG. 7B, occlusion apparatus 200 isillustratively shown in conjunction with catheter 41. Stent S extendsbeyond the bifurcation between the ECA and the ICA and into the CCA.Balloon 202 is deflated and positioned for retrieval. Because balloon202 is disposed on guide wire 201 instead of a traditional, largerdiameter balloon catheter, its cross-sectional diameter is significantlyreduced, and thus the risk that the balloon will snag on stent S isreduced. Resilient wedge 204 further reduces this risk by urging theballoon outward away from the stent during retrieval of guide wire 201and balloon 202. Alternatively, a separate sheath may be advanced overguide wire 201 and occlusion balloon 202 to surround those components,and therefore reduce the risk that the occlusion balloon or guide wirewill snag the stent.

[0070] While preferred illustrative embodiments of the invention aredescribed above, it will be apparent to one skilled in the art thatvarious changes and modifications may be made. The appended claims areintended to cover all such changes and modifications that fall withinthe true spirit and scope of the invention.

What is claimed is:
 1. Apparatus for removing emboli during anangioplasty or stenting procedure, the apparatus comprising: a catheterhaving proximal and distal ends, a lumen extending therethrough, and ablood outlet port in communication with the lumen, the catheter adaptedto be disposed in a patient's carotid artery; an occlusion elementdisposed on the distal end of the catheter and having an opening thatcommunicates with the lumen, the occlusion element having a contractedstate suitable for transluminal insertion and an expanded state whereinthe occlusion element occludes antegrade flow in the vessel; a venousreturn catheter having proximal and distal ends, a lumen extendingtherethrough, and a blood inlet port in communication with the lumen;and tubing that couples the blood outlet port to the blood inlet port.2. The apparatus of claim 1 further comprising a wire having a distalend and a balloon disposed on the distal end, wherein the wire andballoon are sized to pass through the lumen of the catheter.
 3. Theapparatus of claim 1 further comprising a blood filter coupled betweenthe blood outlet port and the blood inlet port.
 4. The apparatus ofclaim 1 wherein the occlusion element is an inflatable member.
 5. Theapparatus of claim 4 wherein the inflatable element has a pear-shapewith a wall thickness that varies along the length of the inflatablemember.
 6. The apparatus of claim 4 wherein a portion of the pear-shapedinflatable member extends beyond the distal end of the catheter in thecontracted position and forms an atraumatic bumper.
 7. The apparatus ofclaim 1 wherein the occlusion element comprises a self-expanding basket.8. The apparatus of claim 1 wherein the catheter comprises: a non-sticktubular member; a layer of wire braid disposed surrounding the non-sticktubular member; and a layer of thermoplastic polymer disposed on thelayer of wire braid.
 9. The apparatus of claim 1 wherein the catheterfurther comprises a second lumen through which the wire and inflatableballoon may be inserted.
 10. The apparatus of claim 1 further comprisinga pump that removes blood through the catheter and reperfuses blood viathe venous return catheter.
 11. The apparatus of claim 2 furthercomprising a resilient wedge affixed to the wire proximal of the balloonto reduce snagging of the balloon following a stenting procedure.
 12. Amethod for removing emboli from a vessel comprising: providing acatheter having proximal and distal ends, a lumen extendingtherethrough, an occlusion element disposed on the distal end, ahemostatic port coupled to the lumen, and a blood outlet port coupled tothe lumen; providing a venous return catheter having proximal and distalends, a lumen extending therethrough, and a blood inlet port coupled tothe lumen; inserting the distal end of the catheter to a positionproximal to the stenosis; inserting the distal end of the venous returncatheter into a remote vein; deploying the occlusion element to occludeantegrade flow through the vessel; causing blood to flow between theblood outlet port and the blood inlet port to induce reverse flow in,and remove emboli from, the vessel.
 13. The method of claim 12 furthercomprising: providing a blood filter; and coupling the blood filter influid communication between the blood outlet port and the blood inletport.
 14. The method of claim 12 further comprising: providing a wirehaving a balloon; while flow is reversed in the vessel, advancing theballoon of the wire into the patient's external carotid artery;inflating the balloon of the wire to prevent reverse flow from theexternal carotid artery from entering the internal carotid artery. 15.The method of claim 12 further comprising, while causing blood to flowbetween the blood outlet port and the blood inlet port, performing aninterventional procedure with an interventional instrument insertedthrough the hemostatic port.
 16. The method of claim 12 wherein theocclusion element comprises a balloon, and deploying the occlusionelement comprises inflating the balloon.
 17. The method of claim 12wherein the occlusion element comprises a self-expanding basket, anddeploying the occlusion element comprises retracting a sheath relativeto the distal end of the catheter.
 18. The method of claim 14 whereinadvancing the balloon of the wire into the patient's external carotidartery comprises advancing the balloon through a separate lumen of thecatheter.
 19. The method of claim 12 further comprising: providing apump; and actuating the pump to increase a rate of flow of blood betweenthe blood outlet port and the blood inlet port.
 20. The method of claim15 wherein performing an interventional procedure with an interventionalinstrument comprises delivering a stent within the vessel and the wirefurther comprises a resilient wedge, the method further comprisingurging the resilient wedge against the stent during removal of the wireand balloon.